The present application claims priority to Japanese Application No. P11-312306 filed Nov. 2, 1999, which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a rotary drum and a magnetic tape recording/reproducing apparatus using the same or more specifically to technology which allows recording density of a magnetic tape to be changed by changing tape/head relative speed and recording density to be increased by solving problems which have occurred in increasing the tape/head relative speed.
2. Related Art Statement
Among magnetic tape recording/reproducing apparatuses, there has been one which reproduces information by means of reproducing heads while recording information on a tape recording medium by means of recording heads.
For instance, a magnetic tape streamer drive unit known as a computer data recording apparatus reproduces information while recording the information to a tape recording medium to check whether or not the information has been correctly recorded. Such function is called as RAW (Read after Write) function. In order to realize such function, a rotary drum is provided with recording heads and reproducing heads and a rotary transformer is provided with recording system channels and reproducing system channels for transmitting signals to the recording heads and for transmitting signals from the reproducing heads.
FIGS. 9 through 11 show one example of a prior art rotary drum for realizing such RAW function, wherein FIG. 9 is a schematic plan view for explaining the positional relationship of the respective heads and FIG. 10 is a schematic side view of the rotary drum.
The rotary drum a is provided with the two recording heads bA and bB and two reproducing heads cA and cB separately with 180xc2x0 of central angle as shown in FIG. 9. The recording head bA has an azimuth angle A and the recording head bB has an azimuth angle B. The reproducing head cA has an azimuth angle A and the reproducing head cB has an azimuth angle B.
The recording heads bA and bB are disposed with a certain gap, e.g., 11 xcexcm, in the direction of a rotary shaft (in the direction of height) of the rotary drum a and the reproducing heads cA and cB are also disposed with a certain gap, e.g., 11 xcexcm, in the same manner with the recording heads bA and bB as shown in FIG. 10. It is noted that FIG. 9 shows the recording heads bA and bB and the reproducing heads cA and cB by arranging in the circumferencial direction in order to represent the respective heads on a plan view.
Thereby, recording tracks Ta having the azimuth angle A and recording tracks Tb having the azimuth angle B are recorded on the magnetic tape d separately with the gap between the recording head bA and recording head bB (gap in the direction of height of the drum, e.g., 11 xcexcm) as shown in FIG. 11.
However, because the track pitch Tp of the recording tracks recorded on the magnetic tape d by the prior art rotary drum a as described above is equal to the gap between the recording heads bA and bB (gap in the direction of height of the drum, e.g., 11 xcexcm) and is constant, it is unable to change the recording density of the magnetic tape d (see FIG. 11).
Then, it is conceivable to dispose two recording heads eA and eB and two reproducing heads cA and cB by separating them by 180xc2x0 of central angle as shown in FIG. 12.
Thereby, the track pitch Tp may be changed by changing tape/head relative speed.
That is, the distance between the recording track Ta and the recording track Tb (track pitch Tp) is determined by the tape/head relative speed. The track pitch Tp increases as the tape/head relative speed increases and the pitch decreases as the speed decreases. Thereby, the recording density of the magnetic tape d may be changed by changing the tape/head relative speed.
However, when the tape/head relative speed is increased to increase the recording density by disposing the two recording heads 6A and 6B by separating by 180xc2x0 of central angle as described above, there has been a problem that the neighboring recording tracks Ta and Tb are liable to overlap.
That is, the rotary drum a sometimes causes precession which bends slightly and helically the recording tracks Ta and Tb formed on the magnetic tape d when spread in plan as shown in FIG. 13.
As it is apparent from FIG. 13, when the rotary drum a causes precession, a locus of an arbitrary point thereof is S-shaped in one turn (360xc2x0) when spread in plan and a locus which bends upward or downward is formed in a half turn (180xc2x0).
Then, when the two recording heads bA and bB create such S-shaped locus by semicircle each (180xc2x0 each), two recording tracks are formed abreast. The locus of one recording head bA becomes the recording track Ta which bulges upward and the locus of the other recording head bB becomes the recording track Tb which bulges downward. Thus, the bulged parts become closer to each other as compared to the other parts and the two recording tracks Ta and Tb overlap each other in some cases.
Accordingly, there has been a problem that even if the track pitch is reduced by disposing the two recording heads bA and bB separately with 180xc2x0 of central angle and by increasing the tape/head relative speed, the track pitch cannot be reduced so much and the increase of the recording density is limited.
Accordingly, it is an object of the invention to provide a rotary drum which realizes a plurality of modes with regard to recording density of a magnetic tape by changing tape/head relative speed and increases the recording density by solving the limit of the increase of recording density implemented by increasing the tape/head relative speed.
It is another object of the invention to provide a magnetic tape recording/reproducing apparatus which realizes a plurality of modes with regard to recording density of a magnetic tape corresponding to different tape/head relative speeds and increases the recording density by solving the limit of the increase of recording density implemented by increasing the tape/head relative speed.
In order to achieve the above-mentioned objects, an inventive rotary drum comprises a pair of recording heads having different azimuth angles and disposed separately with 180xc2x0 of central angle and a second recording head disposed at the same position in the circumferential direction with at least one recording head among the pair of recording heads while leaving a predetermined gap in the direction of height of the rotary drum and having a different azimuth angle from the one recording head.
Accordingly, because the pair of recording heads are disposed separately with 180xc2x0 of central angle on the inventive rotary drum, the plurality of modes may be realized with regard to the recording density of the magnetic tape by varying the tape/head relative speed. Further, because the second recording head is disposed by leaving the certain gap (gap in height) in the direction of height from one recording head, the parallel of the two recording tracks created by such gap in height may be maintained. Therefore, the recording density may be increased by setting a mode so that such gap in height becomes the smallest track pitch.
According to a second aspect of the invention, the drum further comprises a dummy head having almost the same mass with the second recording head at the position separated from the second recording head by 180xc2x0 of central angle, so that it is possible to eliminate the weightwise eccentricity of the rotary drum and to prevent nonuniformity of rotation in rotating the drum.
An inventive magnetic tape recording/reproducing apparatus has a rotary drum comprising a pair of recording heads having different azimuth angles and disposed separately with 180xc2x0 of central angle and a second recording head disposed at the same position in the circumferential direction with at least one recording head among the pair of recording heads while leaving a predetermined gap in the direction of height of the rotary drum and having a different azimuth angle from one recording head. The apparatus has two or more modes with regard to tape/head relative speed of tape recording medium.
Accordingly, because the pair of recording heads are disposed separately with 180xc2x0 of central angle in the inventive magnetic tape recording/reproducing apparatus, the plurality of modes may be realized with regard to the recording density of the magnetic tape by varying the tape/head relative speed. Further, because the second recording head is disposed by leaving the certain gap (gap in height) in the direction of height from one recording head, the parallel of the two recording tracks created by such gap in height may be maintained. Therefore, the recording density may be increased by setting a mode so that such gap in height becomes the smallest track pitch.